Liposome-Based Immunosensors. 1. Influence of Hapten Spacer Length on Liposome Binding Efficiency

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Abstract
The effect of spacers on the binding of atrazine-tagged liposomes to anti-atrazine antibodies was studied. Atrazine derivatives with alkyl spacers of different length (C4, C6, C8 and C12) were synthezised and conjugated to dipalmitoyl phosphatidyl ethanolamine. The conjugates were incorporated into liposomal membranes of DPPC/DPPG/cholesterol containing ascorbic acid as entrapped marker. Tagged liposomes were bound to a monoclonal anti-atrazine antibody immobilized on a nitrocellulose membrane, destroyed by the addition of surfactant and the marker was detected electrochemically using printed thick-film electrodes. Our results show that liposomes incorporating a hapten with short alkyl spacer binds better to the immobilized antibody. These results will allow optimization of liposomes as an enhancement system in electrochemical or optical biosensors.